DESCRIPTION: In this proposal, Dr. Darby describes experiments focused on the mechanisms involved in the recruitment of the transcriptional machinery to a 5S rRNA gene by the specific factor TFIIIA. A protein has been identified, TIP21 which interacts with the C-terminus of TFIIIA. This protein has homology with individual subunits of both yeast RNA polymerase II and III. Dr. Darby wishes to test any functional role of TIP21 in 5S rRNA gene transcription in vitro and in vivo using standard approaches (immunodepletion, ribozyme ablation) and to examine structure-function (Far-Western, two hybrid).